Hi there,

I've written about this a good deal in previous posts, and contributed to a couple /r/askhistorians podcast episodes that might be of interest to you on this very topic:

• Episode 1
• Episode 2
• This thread on administrative divisions in the Ottoman empire and the sectarian composition of the Arab Middle East.
• The partitioning of the empire (NB, this thread and all subsequent ones below were undertaken prior to some additional and more specific research that I did in preparation for the podcast, and therefore aren't as thorough as what I might now write or what I discussed in the podcasts)
• Treaties dealing with partition.
• The contradictions of Balfour, Sykes-Picot and Hussein-McMahon.
• The specific contradiction (or not) of Hussein-McMahon and Sykes-Picot re the Hashemites

I've also written some posts on the emergence of "the current mess in the Middle East", my own view is that the partition of the Ottoman Empire is an important part of that, but it's not causal and it's probably massively overstated. For one thing, such explanations tend to assume that there was some version of the borders in the Middle East that might have prevented such conflict-- there was not. For another it elides that for most of the 20th century you could not have characterized the countries that are currently a "mess" as being a mess. Iraq looked pretty good in the 60s and 70s, for instance. Nor are such conflicts intractable centuries-old issues that will never go away as evidenced by the end of the civil conflict in Lebanon (even if those issues continue to define Lebanese politics.)

I've written some of my thoughts on that and issues related to "the current mess" in these two threads:

• When did the fundamental differences between Sunni, Shiites and others develop? What were the catalysts for these differences?
• Can someone explain the history of the middle east, and the conflicts within them?
• This thread from a Friday-Free-For-All on ISIS may also be of interest.

I think those will more or less cover the questions you've raised so far, I'm happy to discuss any followup questions you might have.